Mabch 23, 1906.] 



SCIENCE. 



449 



a photographic action which is just as in- 

 tense in the ultra violet as in the green, it 

 would seem that the corona is very rich in 

 ultra-violet rays. The following coronal 

 lines are seen at approximately, AA3381, 

 3388, 3455, 3643, 3984, 4228, 4565, 4618 

 and the 'coronium' line at A5303. 



2. Flat Grating, with 15,000 lines to the 

 inch, and a ruled surface 3| x 6 inches. 

 The lens is a Clark five-inch visual with a 

 focal length of about six feet. On the 

 photographs the distance from D^ to H is 

 eight inches. In the flash spectrum lines 

 can be seen beyond D toward the red al- 

 most to C. This is the end of the spec- 

 trum most desired, and the focus is excel- 

 lent from F to the extreme of the red. 

 The green (coronium) ring also appears 

 on the plates taken near mid-totality. 



Observations of Badial Velocities: Edwin 



B. Frost. 



The four principal programs of observa- 

 tions with the Bruce spectrograph of the 

 Yerkes Observatory are: (1) standard ve- 

 locity stars; (2) stars of Orion type; (3) 

 visual binaries; (4) miscellaneous variable 

 stars. About 500 plates of over 100 stars 

 of program (2) have been measured (many 

 in duplicate) ; three or more satisfactory 

 plates have been obtained of 135 stars of 

 the Orion type, and one or two plates of 

 forty more. 



It is important to secure at this epoch 

 good determinations of the sight-line ve- 

 locity component for visual binaries of 

 program (3). With Burnham's assistance 

 an observing list was compiled containing 

 120 stars known to be binary, and bright 

 enough to be observable with the Bruce 

 spectrograph, at least with one prism. 

 Preference was given to pairs differing in 

 magnitude sufficiently to prevent confusion 

 of spectra, and for which the brighter com- 

 ponent would have fairly sharp lines. 



The writer's measurements of P Cygni 

 show that the strong and broad bright com- 

 ponents of the hydrogen and helium lines 

 have only a very small displacement, cor- 

 responding to a radial velocity of about 

 12 km. per second of approach; while the 

 dark components, sharply defined at each 

 margin, and comparatively narrow, yield 

 very large displacements toward the violet, 

 differing for hydrogen and helium. If 

 interpreted by Doppler's principle, the 

 velocities (approach) would be about 190 

 km. for hydrogen and 150 km. for helium; 

 the three blue silicon lines seem to have no 

 bright components, and from these a con- 

 sistent value of about 80 km. (approach) 

 is derived. An attempt to account for 

 these differences as a result of overlapping 

 of the dark and bright lines has not yet 

 been successful. A comparison with Belo- 

 polsky's observations of this star made in 

 1899 indicates that the displacements are 

 not variable. Physical causes may be re- 

 sponsible for this remarkable spectrum. 



Spectrograms of the variable star R T 

 Cygni, obtained in conjunction with Park- 

 hurst, when the star was of magnitude 7.5, 

 showed bright Ey and Eh with an ex- 

 posure as short as 45 minutes. These 

 bright lines were very strongly displaced 

 toward the violet, corresponding to an ap- 

 proaching radial velocity of 100 km. per 

 second. It now seems probable that this 

 did not vary during the first half of De- 

 cember, 1905, which period included the 

 five plates obtained. 



It is possible that variations occur in the 

 bright lines of Pleione, which were very 

 weak, if present, on three plates recently 

 obtained, although they were shown on 

 spectrograms taken by the writer at Pots- 

 dam in 1891, and on Harvard plates. The 

 spectrum of a Columbce is peculiar, and fi. 

 Orionis has been found to be a spectro- 

 scopic binary. 



